Transmitter unit comprising a transmission coil and a temperature sensor

ABSTRACT

The invention relates to a transmitter unit (12) comprising a housing (20), a transmitter coil (18) arranged in the housing (20) for inductively transferring electrical energy to a receiver unit (14) which is provided with a receiver coil (16) and is arranged in the tissue (2) of the body (1) of a patient when the housing (20) having a contact surface (22) is placed on the body (1), and comprising a control device (30) for controlling the operation of the transmitter coil (18). According to the invention, a temperature sensor (26) is provided in the transmitter unit for determining a heating of the tissue (2) of the body (1) caused by the inductive transfer of electrical energy to the receiver unit (14). The invention also relates to methods for determining the temperature (TKorr) of the tissue (2) of a body (1) on a surface (38), by which electrical energy is inductively transmitted for supplying an electrical consumer arranged in the tissue (2) of the body (1), and to a method for inductively transferring electrical energy.

BACKGROUND Field

The invention relates to a transmitter unit comprising a housing,comprising a transmitter coil disposed in said housing for inductivelytransferring electrical energy to a receiver unit, which is disposed ina part of the body of a person, in particular a patient, e.g. in thetissue of a body of a patient, and comprises a receiver coil, when acontact surface of said housing is in contact with the body, andcomprising a control device for controlling the operation of thetransmitter coil.

The invention also relates to a method for determining the localtemperature of a body of a person, in particular a patient, on asurface, e.g. the temperature of the tissue of the body on a surface,through which electrical energy for supplying an electrical consumerdisposed in the tissue of the body is inductively transferred and to amethod for inductively transferring electrical energy. The invention inparticular relates to a method for determining the temperature on asurface in an apparatus for inductively transferring energy. Theinvention further relates to an apparatus which is operated according toa method according to the invention as well as the use of the methodaccording to the invention.

Description of the Related Art

In the medical field, methods for inductively transferring energy, inwhich an energy store in the form of a rechargeable battery disposedinside a body can be charged by inductive means, are already well-knownin the state of the art (DE 10 2016 106 683 A1). For this purpose, areceiver coil disposed in a receiver unit inside the body of a patientcooperates with a transmitter coil disposed in a transmitter unitoutside the body. Between the receiver coil and the transmitter coil,which are positioned at a defined, relatively small distance to oneanother, there is human tissue or the skin of the patient. During theoperation of the transmitter coil, the tissue of the patient between thereceiver unit and the transmitter unit is warmed, in particular as aresult of thermal losses in the transmitter unit and in the receiverunit. The level of warming is limited for health reasons and may notexceed a certain amount.

SUMMARY

The object of the invention is to enable the inductive transfer ofelectrical energy to a powerful electrical consumer or electrical energystore disposed, for example, in the body of a patient, without damagingthe tissue of the patient.

This object is achieved by devices, systems, and methods describedherein.

Advantageous embodiments of the invention are described herein.

The invention is based on the idea that monitoring the temperature ofthe surface of a patient in the region of direct contact with thetransmitter unit makes it possible to infer information about thewarming of the tissue of the patient.

One finding of the invention is that the measurement signals of atemperature sensor, which is disposed as close as possible to theto-be-measured surface, are affected by the inductive transfer ofelectrical energy. It is evident that, during operation of thetransmitter coil, not only the (human) tissue or the skin surface of thepatient is warmed, but that the magnetic fields produced by thetransmitter coil also warm the temperature sensor or its leads, whichresults in a measurement error. Taking into account a not-to-be-exceeded(limit) temperature of the tissue in the transfer region of theapparatus, this then means that the operation of the transmitter coil isnot optimized yet, or the registered temperature does not correspond tothe actual temperature on the to-be-measured surface of the patient.

The invention has the advantage that it makes optimum use of theforeseen (allowable) maximum temperature increase of the tissue of thepatient in the effective region of the transmitter unit or thetransmitter coil, and thus makes it possible to optimize or maximize thetransfer of energy into the receiver coil. This then enables shortcharging times for an electrical energy store, e.g. in the form of arechargeable battery, disposed in the body of the patient, for example,or the possibility of reducing the time the externally disposedtransmitter unit or transmitter coil is worn on the body.

One idea of the invention is that the component of the warming of thetemperature sensor caused by the fields of the transmitter coil of thetransmitter unit is taken into account when the temperature of theto-be-measured surface is registered. Taking into account the componentof the warming of the temperature sensor caused by the (magnetic) fieldsemitted by the transmitter coil therefore reduces the temperature on thesurface determined by the temperature sensor, which results in longeroperating times, and/or makes it possible to set stronger magneticfields of the transmitter coil, before a specific not-to-be-exceededtemperature limit value on the to-be-measured surface is actuallyreached.

In a variant of the method as described thus far, it can be providedthat the component of the warming of the temperature sensor or its inputleads is taken into account as a fixed value resulting from taking intoaccount a given maximum operating time of the apparatus and givenenvironmental parameters. This means that it has been determined, inparticular on the basis of series of tests, by what amount oftemperature the temperature sensor is warmed when it is exposed to atypical maximum operating time of the transmitter coil, taking intoaccount a typical maximum outside temperature, for example. If thisvalue is 0.8 Kelvin, for example, this maximum temperature increase ofthe temperature sensor (0.8 Kelvin) is subtracted from the respectivevalue of the temperature on the surface currently registered by thetemperature sensor, to thereby infer the actual maximum prevailingtemperature on the surface.

In a further variant modified from the variant described above, anactually existing warming of the temperature sensor resulting from theoperation of the transmitter coil can be taken into account bydetermining the component of the warming of the temperature sensortaking into account the registered temperature progression of the sensedsurface after the operation of the transmitter coil of the apparatus hasbeen stopped. This means that, after the operation of the transmittercoil of the apparatus is stopped, the temperature sensor continues toregister the temperature on the to-be-measured surface and delivers itas input values to the control device of the apparatus. The actuallyexisting temperature on the to-be-measured surface at the time theoperation of the transmitter coil is stopped can be inferred using thetemperature drop that occurs over time and is caused, on the one hand,by the no longer occurring transfer of heat into the human body and, onthe other hand, by the heat dissipation from the temperature sensor.

In a further development of this method, it is provided that theoperation of the transmitter coil is stopped periodically. Thetemperature on the to-be-measured surface of the patient can thus bemonitored throughout the entire charging phase or the phase in whichenergy is transferred from the transmitter coil to the receiver coil.

There are a number of different ways to infer the actual temperature ofthe to-be-measured surface. In a first, particularly preferred method,the component of the warming of the temperature sensor caused by theoperation of the transmitter coil is determined on the basis of amathematical function taking into account known parameters of thetemperature sensor and, if applicable, environmental parameters. Knownparameters of the temperature sensor are in particular understood to beits heat storage capacity, its placement inside the housing of thetransmitter unit, and thus its heat dissipation or cooling.Environmental parameters are in particular understood to be the externalambient temperature in the region of the transmitter unit and, ifapplicable, the current body temperature of the patient. The mentionedparameters of the temperature sensor and the apparatus or the housing ofthe apparatus and the ambient temperature can be brought into amathematical relationship, for example using series of tests, such that,for example, a specific cooling function of the temperature sensor isestablished at a specific ambient temperature. This function cantherefore be used to extrapolate or estimate the actual temperature onthe to-be-measured surface at the time the transmitter coil is switchedoff.

In an alternative configuration of the method, however, it can also beprovided that the temporal progression of the temperature registered bythe temperature sensor after the transmitter coil is switched off iscompared to curve progressions stored in the control device and, if itmatches or approximates a stored curve progression, the actualtemperature in the region of the to-be-measured surface at the time thetransmitter coil is switched off can be inferred.

For a further optimization of the energy transfer to shorten chargingtimes or to achieve the highest possible charging rates for theelectrical energy store disposed in the patient, it is proposed that theapparatus for inductively transferring energy is controlled on the basisof the determined temperature, and that the transmitter coil isperiodically not operated to avoid the occurrence of excessively hightemperatures, wherein the duration of the operating breaks of thetransmitter coil is based on the determined temperature on the surface.This means that the length of the operating breaks is selected to besuch that they last only until the registered temperature is at aspecific minimum separation from the limit value. The temperature on theto-be-measured surface is thus always kept just below the limittemperature, which overall enables an optimization of the energytransfer. Alternatively, it is also possible to throttle or adjust thetransmission power to keep the temperature constant without operatingbreaks.

The invention also includes an apparatus for inductively transferringenergy comprising a transmitter coil disposed in a housing, wherein thehousing can be positioned at least in indirect contact with theto-be-measured surface, and wherein the apparatus is operated accordingto a method, in which the component of the warming of the temperaturesensor is determined taking into account the registered temperatureprogression of the sensed surface after the operation of the transmittercoil of the apparatus is stopped. According to the invention, thisapparatus comprises a temperature sensor, which can be exposed to theelectromagnetic field of the transmitter coil so that said sensor isdisposed in an operative connection with said coil. The apparatus cancomprise an algorithm for determining the component of the warming ofthe temperature sensor or its input leads caused by the transmittercoil.

For the sake of making the apparatus as compact as possible, it ispreferably provided that the temperature sensor is of an SMD design.

Lastly, the invention also includes the use of a method according to theinvention as described thus far for determining the skin and/or tissuetemperature in a human body during a transfer of energy into the humanbody, in particular with a VAD (ventricular assist device) system.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention emerge fromthe following description of preferred design examples. These are shownschematically in the drawings and are described below.

The figures show:

FIG. 1 an apparatus for inductively transferring energy comprising atransmitter coil and comprising a temperature sensor, which is used forinductively transferring energy into a receiver unit having a receivercoil in a VAD system disposed in a human body;

FIG. 2 a first diagram with the temporal progression of a temperature Tregistered by the temperature sensor in the apparatus for inductivelytransferring energy and with a limit temperature T_(Grenz), and

FIG. 3 a second diagram with the temporal progression of a temperature Tregistered by the temperature sensor in the apparatus for inductivelytransferring energy and with a limit temperature T_(Grenz).

DETAILED DESCRIPTION

The same elements or elements having the same function are provided withthe same reference signs in the figures.

FIG. 1 shows the essential components of an apparatus 10 for inductivelytransferring energy on a receiver unit 14 disposed in the body 1 of apatient and having a receiver coil 16 in a highly simplified manner. Theapparatus 10 is in particular a component of a cardiac support system inthe form of a so-called ventricular assist device system (VAD system)100. The VAD system 100 in particular includes a pump disposed in thebody 1 of the patient, which supports the patient's heart function. Inthe body 1 of the patient, this pump is operated with electrical energyfrom an electrical energy store not shown in FIG. 1 , e.g. arechargeable battery, which is connected to the receiver unit 14. Thiselectrical energy store has to be charged due to the energy consumptionof the pump. By inductively transferring energy into the receiver unit14 by means of the apparatus 10, the electrical energy store connectedto the receiver unit 14 is charged.

The apparatus 10 comprises a transmitter unit 12 outside the body 1 ofthe patient and the receiver unit 14 with the receiver coil 16 disposedinside the body 1 of the patient. It should be noted that the receiverunit 14 may in principle comprise a plurality of receiver coils 16.

Between the transmitter unit 12 and the receiver unit 14 there is humantissue 2 or the skin of the patient. The receiver coil 16 is disposed inoperative connection with the electrical energy store to be charged. Thereceiver coil 16 cooperates with a transmitter coil 18 disposed in thetransmitter unit 12. The transmitter coil 18 is disposed inside ahousing 20 of the transmitter unit 12, whereby the housing 20 isdisposed at least in indirect contact with the body 1 or the tissue 2 inthe region of a contact surface 22 of the housing 20.

The transmitter coil 18 has a coil winding 17, which comprises conductorloops disposed around a coil axis 19 that passes through the contactsurface 22. The coil winding 17 of the transmitter coil 18 is located ona transmitter coil carrier 21, which extends in a planar manner andthrough which the coil axis 19 passes, and which has a carrier surfacethat faces the contact surface 22 of the housing 20 for the coil turnsof the transmitter coil 18.

To operate the apparatus 10, it is also necessary for the receiver coil16 and the transmitter coil 18 to be aligned with one another in orderto be able to produce a magnetic field when current is supplied to thetransmitter coil 18. The field lines 24 of this magnetic field, whichare shown in FIG. 1 , lead to the induction of an electrical voltage andthus to the flow of an electrical current in the receiver coil 16, whichcan then be used to charge the electrical energy store.

During operation of the transmitter coil 18, the tissue 2 of the body 1located between the transmitter unit 12 and the receiver unit 14 iswarmed by the loss-related warming of the transmitter unit 12 and thereceiver unit 14. This warming of tissue 2 has to be limited to avoidphysical impairments or damage and/or to comply with legal standards.

For this purpose, it is provided that the temperature of the tissue 2 inthe region of contact of the housing 20 of the transmitter unit 12 withthe tissue 2 is monitored by means of a temperature sensor 26 in theregion of a measurement surface 38 on the surface of the tissue 2.

The temperature sensor 26 is disposed in the housing 20 of thetransmitter unit 12 on a side 23 of the transmitter coil 18 facing thecontact surface 22.

To make the design as compact as possible, it is in particular providedthat the temperature sensor 26 is designed as an SMD component or an SMDassembly. The temperature sensor 26 is connected to a control device 30of the transmitter unit 12 via an electrical lead 28. The control device30 is also used to control the transmitter coil 18 via a lead 32. Afurther lead 34 connects the control device 30 to a further temperaturesensor 36, which is configured to register the ambient temperatureoutside the transmitter unit 12.

As can be seen in FIG. 1 , both the temperature sensor 26 and, ifapplicable, the lead 28 are disposed in operative connection with themagnetic field lines 24 of the transmitter coil 18. As a result, duringoperation of the transmitter coil 18, not only the tissue 2 is warmed,in particular by the lost heat from the transmitter unit 12 and thereceiver unit 14, but also the temperature sensor 26 or the lead 28, inparticular by the magnetic field of the transmitter coil 18, which canlead to the temperature sensor 26 heating up more than the surroundingtissue 2. This in turn has the consequence that the temperature increaseof said components leads to a measurement error, which manifests itselfin that the temperature T registered by the temperature sensor 26 in theregion of the measurement surface 38 is falsified or increased by themeasurement error.

To detect or take into account this measurement error or to register theactual temperature T on the measurement surface 38 of the body 1, thetransmitter coil 18 is operated in a specific manner. For clarification,reference is made to FIG. 2 .

FIG. 2 shows the temperature T registered by the temperature sensor 26in the apparatus 10 at the time t as a curve progression A. Thetemperature sensor 26 transmits the temperature T registered at the timet to the control device 30.

The temperature T increases slightly in the period between t₀ and t₁.The increase in temperature T can be explained by the fact that, duringoperation of the transmitter coil 18, both the temperature in the tissue2 and the temperature in the temperature sensor 26 or the lead 28 isincreased by the effect of the temporally changing magnetic fieldproduced by the transmitter coil 18, which causes eddy currents.However, the temperature T is below a limit temperature T_(Grenz) thathas to be observed. At the time point t₁, the operation of thetransmitter coil 18 is now stopped by the control device 30. The curveprogression A then shows that the temperature T, which continues to beregistered by the temperature sensor 26 and delivered to the controldevice 30 as an input quantity, decreases with the decay curve 40.

The curve progression A after the time point t₁ results from both thenow absent warming of the tissue 2, or its cooling, and from the heatdissipation or cooling of the temperature sensor 26 and the lead 28.

An algorithm with a mathematical function is stored in the controldevice 30 of the transmitter unit 12 or the apparatus 10, which makes itpossible to infer the actual temperature T in the region of themeasurement surface 38 at the time point t₁ based on the values of thetemperature T after the time point t₁, for example by extrapolation fromthe cooling rate V_(K) at a time point t₂ after the time point t₁. Thismakes use of the fact that, due to its size, the temperature sensor 26has a significantly lower heat storage capacity than the surroundingtissue 2 and the surface of the housing 20. As a result, there is adynamic drop in the temperature T immediately after the transmitter coil18 is switched off at the time point t₁. Once this temporaryequalization process is completed at the time point t₂, the temperaturesensor 26 registers the actual temperature T of the tissue 2, becausethe low heat storage capacity of the temperature sensor 26 has been“discharged”. The mentioned extrapolation of the cooling curve at theswitch-off time t₁ can therefore be used to infer the actual temperatureat the switch-off time t₁. The additional warming of the temperaturesensor 26 is thus taken into account or eliminated.

Alternatively, it can be provided that the curve progression A after thetime point t₁ is compared to curve progressions stored in the controldevice 30, and, if it matches or approximates a stored curveprogression, the respective temperature T_(Korr) at the measurementsurface 38 of the body 1 at the time point t₁ is inferred. Thedifference between the corrected temperature T_(Korr) on the measurementsurface 38 and the temperature T registered at the time point t₁ is thecomponent ΔW caused by the warming of the temperature sensor 26 and thelead 28.

As soon as the temperature T on the measurement surface 38, which hasbeen corrected by the amount of warming of the temperature sensor 26 orthe lead 28 caused by the operation of the transmitter coil 18, has beendetermined, the control device 30 again actuates the transmitter coil 18in order to enable a further transfer of energy. In order to enablecontinuous monitoring of the (actual) temperature T on the measurementsurface 38, the switching off or switching on of the transmitter coil 18as described thus far is preferably carried out periodically, i.e. atregular intervals.

FIG. 3 shows a diagram that illustrates a simplified measurementprocedure. Here, the temperature T registered by the temperature sensor26 is again shown over the time t. A continuous, i.e. uninterrupted,operation of the transmitter coil 18 is assumed. The values of thetemperature T transmitted by the temperature sensor 26 to the controldevice 30 are indicated by the curve progression A. The curveprogression A_(K) shows a corrected curve progression A taking intoaccount a fixed value ΔF as the component ΔW, which is assumed to be themaximum possible measurement error resulting from the warming of thetemperature sensor 26 and the lead 28 due to the warming caused by theoperation of the transmitter coil 18. In other words, this means thatthe control device 30 assumes that the temperature T calculated usingthe A_(K) is the highest possible temperature that can be present on themeasurement surface 38.

Of course, in both methods it is respectively assumed that the operationof the apparatus 10 or the transmitter coil 18 is stopped when a limittemperature T_(Grenz) is approached, for example until the determinedtemperature T has a specific separation from the limit temperatureT_(Grenz).

The methods as described thus far can be altered or modified in avariety of ways without departing from the idea of the invention. Itshould in particular be noted that the described methods are not limitedto use in a VAD system 100.

In summary, the following preferred features of the invention should inparticular be noted:

A transmitter unit 12 comprises a housing 20 and a transmitter coil 18disposed in said housing 20 for inductively transferring electricalenergy to a receiver unit 14, which is disposed in the tissue 2 of thebody 1 of a patient and comprises a receiver coil 16, when a contactsurface 22 of said housing 20 is in contact with the body 1. Thetransmitter unit 12 comprises a control device 30 for controlling theoperation of the transmitter coil 18. The transmitter unit comprises atemperature sensor 26 for determining a local warming of the body 1caused by the inductive transfer of electrical energy into the receiverunit 14. The invention also relates to methods for determining thetemperature (T_(Korr)) of a body 1 on a surface 38 through whichelectrical energy for supplying an electrical energy store or anelectrical consumer disposed in the body 1 is inductively transferredand to a method for inductively transferring electrical energy.

The invention relates, in particular, to the aspects specified in thefollowing clauses:

-   -   1. Method for determining the temperature (T) on a surface (38)        in apparatus (10) for inductively transferring energy, wherein        the apparatus (10) comprises a transmitter coil (18) disposed in        a housing (20) and the housing (20) is disposed at least in        indirect contact with the to-be-measured surface (38), and        comprising a temperature sensor (26) for registering the        temperature (T) of the surface (38), wherein the temperature        sensor (26) and, if applicable, the electrical lead (28) of said        sensor is disposed in operative connection with the transmitter        coil (18), such that, during operation of the transmitter coil        (18), the temperature sensor (26) and, if applicable, the        electrical lead (28) of said sensor is warmed by the fields        emitted by the transmitter coil (18), so that the        temperature (T) registered by the temperature sensor (26)        includes a component (ΔW) that results from the warming of the        temperature sensor (26) and, if applicable, the electrical lead        (28) of said sensor by the transmitter coil (18), and wherein        the component (ΔW) resulting from the transmitter coil (18) is        taken into account in the registering of the temperature (T) of        the measurement surface (38).    -   2. Method according to clause 1, characterized in that that the        component (ΔW) is taken into account as a fixed value (ΔF),        which is obtained by taking into account a given maximum        operating time of the apparatus (10) and given environmental        parameters.    -   3. Method according to clause 1, characterized in that the        component (ΔW) of the warming is determined taking into account        the registered temperature progression (A) of the sensed surface        (38) after the operation of the transmitter coil (18) of the        apparatus (10) is stopped.    -   4. Method according to clause 3, characterized in that the        operation of the transmitter coil (18) is stopped periodically.    -   5. Method according to clause 3 or 4, characterized in that the        component of the warming (ΔW) is determined on the basis of a        mathematical function, taking into account known parameters of        the temperature sensor (26), such as its heat storage capacity        storage capacity, and, if applicable, environmental parameters.    -   6. Method according to clause 3 or 4, characterized in that the        component of the warming (ΔW) is based on a comparison of the        temperature progression (A) on the sensed surface (38) with        stored curve progressions.    -   7. Method according to any one of clauses 1 to 6, characterized        in that the apparatus (10) for inductively transferring energy        is controlled on the basis of the determined temperature (T) and        the transmitter coil (18) is periodically not operated to avoid        the occurrence of excessively high temperatures (T), wherein the        duration of the operating breaks of the transmitter coil (18) is        based on the determined temperature (T) on the surface (38).    -   8. Apparatus (10) for inductively transferring energy,        comprising a transmitter coil (18) disposed in a housing (20),        wherein the housing (20) can be positioned at least in indirect        contact with a to-be-measured surface (38), wherein the        apparatus (10) is operated according to a method according to        any one of Clauses 3 to 7, characterized in that a temperature        sensor (26) is disposed in operative connection with the        transmitter coil (18), and that the apparatus (10) comprises an        algorithm for determining the component (ΔW) of a warming of the        temperature sensor (26) and, if applicable, the lead (28) of        said sensor caused by the fields emitted by the transmitter coil        (18).    -   9. Apparatus according to clause 8, characterized in that the        temperature sensor (26) is of an SMD design.    -   10. Use of the method according to any one of clauses 1 to 7 for        determining the skin and/or tissue temperature of a human body        (1) during an energy transfer in the human body (1), in        particular in a VAD system (100).

LIST OF REFERENCE SIGNS

-   1 Body-   2 Human tissue-   10 Apparatus-   12 Transmitter unit-   14 Receiver unit-   16 Receiver coil-   17 Coil winding-   18 Transmitter coil-   19 Coil axis-   20 Housing-   21 Transmitter coil carrier-   22 Contact surface-   23 Side-   24 Field line-   26 Temperature sensor-   28 Electrical lead-   30 Control device-   32 Lead-   34 Further lead-   36 Further temperature sensor-   38 Measurement surface-   40 Decay curve-   42 Section-   100 Ventricular assist device (VAD) system-   A Curve progression-   A_(K) Corrected curve progression-   T Temperature-   T_(Grenz) Limit temperature-   T_(Korr) Corrected temperature-   t Time-   V_(K) Cooling rate-   ΔW Component-   ΔF Fixed value

The invention claimed is:
 1. A transmitter unit comprising: a housingcomprising a transmitter coil configured to inductively transferelectrical energy to a receiver unit disposed in a part of a body of apatient in response to a contact made between a contact surface of thehousing and the body of the patient, the receiver unit comprising areceiver coil; a temperature sensor configured to determine an increasein local temperature of the body caused by the inductive transfer ofelectrical energy to the receiver unit; and a control device configuredto control operation of the transmitter coil based at least in part onthe increase in local temperature of the body, wherein the controldevice stores a temperature determination routine configured todetermine a local temperature at a surface of the body based at least inpart on temperature measurement signals of the temperature sensor;wherein the temperature determination routine is configured to stop theoperation of the transmitter coil at a first time point and contains analgorithm configured to calculate the local temperature based at leastin part on a decay curve determined based at least in part on thetemperature measurement signals from the temperature sensor after thefirst time point, wherein the temperature determination routine isconfigured to account for warming of the temperature sensor caused byeddy currents.
 2. The transmitter unit of claim 1, wherein thetransmitter coil is disposed in the housing and the temperature sensoris positioned between the transmitter coil and the contact surface. 3.The transmitter unit of claim 2, wherein the transmitter coil comprisesconductor loops configured to form a coil winding around a coil axisthat passes through and orthogonal to the contact surface.
 4. Thetransmitter unit of claim 3, wherein the conductor loops are disposed onor in a transmitter coil carrier extending in a planar manner andparallel to the contact surface.
 5. The transmitter unit of claim 4,wherein the transmitter coil carrier comprises a carrier surface whichfaces the contact surface of the housing.
 6. The transmitter unit ofclaim 1, wherein the temperature determination routine is configured toaccount for an operating state of the transmitter coil.
 7. Thetransmitter unit of claim 1, wherein the algorithm is configured tocalculate the local temperature at the surface of the body based atleast in part on extrapolation of the decay curve from a second timepoint following the first time point to the first time point.
 8. Thetransmitter unit of claim 7, wherein the algorithm is configured tolinearly extrapolate the progression of the decay curve from a secondtime point to the first time point.
 9. The transmitter unit of claim 1,wherein the algorithm is configured to subtract a fixed correction valuefrom temperature values corresponding to the temperature measurementsignals.
 10. The transmitter unit of claim 1, wherein the control devicestores a shutdown routine configured to stop the operation of thetransmitter coil, wherein the shutdown routine is configured to preventor reduce the inductive transfer of electrical energy to the receiverunit when the local temperature determined by the temperaturedetermination routine exceeds a threshold value.
 11. The transmitterunit of claim 1, wherein the temperature sensor is at least one of: asurface-mount-device component, a temperature-dependent measuringresistor, and a thermocouple.
 12. A system comprising: a temperaturesensor; a transmitter coil; a memory storing computer-readableinstructions; a processor configured to communicate with the temperaturesensor, the transmitter coil, and the memory, wherein thecomputer-readable instructions, when executed, cause the processor to:prevent an inductive transfer of electrical energy from the transmittercoil at a first time point; determine temperatures of a surface of abody at a plurality of time points following the first time point;determine a decay curve based at least in part on the temperaturesmeasured at the plurality of time points following the first time point;and calculate a local temperature of the surface of the body based atleast in part on the decay curve and an algorithm configured to accountfor an effect of the inductive transfer of electrical energy from thetransmitter coil to an electrically powered device.
 13. The system ofclaim 12, wherein the algorithm is configured to determine the localtemperature of the surface of the body at least in part by extrapolatinga progression of a section of the decay curve from a second time pointfollowing the first time point to the first time point.
 14. The systemof claim 13, wherein the algorithm is configured to extrapolate theprogression of the section of the decay curve based at least in part ona comparison of the decay curve with one or more decay curveprogressions stored in the memory.
 15. The system of claim 13, whereinthe algorithm is configured to linearly extrapolate the progression ofthe decay curve from the second time point to the first time point. 16.The system of claim 13, wherein the preventing the inductive transfer ofelectrical energy from the transmitter coil at the first time point, themeasuring the temperatures at the surface at the plurality of timepoints following the first time point, the determining the decay curvefrom the temperatures measured at the plurality of time points followingthe first time point, and the calculating the local temperature at thesurface of the body based at least in part on the decay curve and thealgorithm configured to account for an effect of inductive transfer ofelectrical energy from the transmitter coil to the electrically powereddevice are repeated continuously.
 17. A method for determining a localtemperature at a surface of a human body, wherein electrical energy foran electrical energy storage or an electrically powered device disposedin the body is inductively transferred through the surface, the methodcomprising: preventing an inductive transfer of the electrical energy ata first time point; determining temperatures measured at the surface ata plurality of time points following the first time point; determining adecay curve based at least in part on the temperatures measured at thesurface at the plurality of time points following the first time point;and calculating the local temperature at the surface based at least inpart on the decay curve and an algorithm accounting for an effect of theinductive transfer of electrical energy to the electrical energy storageor the electrically powered device.
 18. The method of claim 17, whereinthe algorithm is configured to extrapolate a progression of a section ofthe decay curve from a second time point following the first time pointto the first time point.
 19. The method of claim 18, wherein thealgorithm is configured to extrapolate the progression of the section ofthe decay curve based at least in part on a comparison of the decaycurve to one or more decay curve progressions stored in a data memory.20. The method of claim 18, wherein the algorithm is configured tolinearly extrapolate the progression of the decay curve from the secondtime point to the first time point.